Split Loop

Removes smells

Symptom

A single loop body that mixes filter, map, reduce, and side-effect concerns; the agent verifying any change must trace all concerns through the same iteration.

Goal

Each loop does one thing; the agent reasons about one concern per loop and can replace each loop independently with a pipeline.

Before the refactoring

let totalSalary = 0;
let youngest = Infinity;
for (const p of people) {
  if (p.age < youngest) youngest = p.age;
  totalSalary += p.salary;
}

After the refactoring

const totalSalary = people.reduce((s, p) => s + p.salary, 0);
const youngest    = Math.min(...people.map(p => p.age));

Example source: Illustrative example written for this site, not a quotation from any source.

Pressure

The agent's per-line reasoning must account for every concern the loop body addresses; changing one concern risks silent interaction with the others.

Tradeoff

Two loops over the same collection cost more per iteration than one; for hot paths the runtime overhead matters and the agent verifying performance must measure.

Relief

Each loop body holds one state machine the agent simulates without interleaving; an edit to one job no longer needs the other job's tokens loaded to predict the loop's output.

Trap

Splitting loops whose concerns share per-iteration state — accumulator-of-running-difference, look-behind logic — fragments coupled state the agent must now re-derive in each split.